In just three matches this season, the Chiefs have used 30 players, a number that will increase this week with Andrew Horrell favoured to fill the void at centre and form a third midfield combination.

Charlie Ngatai and Robbie Fruean were the Chiefs' preferred midfield pairing in scratchy wins over the Crusaders and Highlanders. Both, however, will sit out the trip to Perth and South Africa through injury.

Their absence leaves holes, predominately at centre. The Chiefs aren't about to dwell on player losses, though.

They've introduced six debutants this year and with seemingly endless options it's easy to see why the defending champions -New Zealand's only unbeaten team - see this overseas venture as a chance to strengthen resolve.

''Rather than put us in a spot of trouble it's created an opportunity to get guys game-time,'' assistant coach Wayne Smith said ahead of his 19th journey to South Africa.

All Blacks centurion Mils Muliaina - struggling with an on-going elbow injury - and Tim Nanai-Williams are contenders for the midfield.

Muliaina was selected with the brief of covering centre, wing and fullback, while Nanai-Williams also frequently displayed his explosive attributes in the 13 jersey.

But having proved his worth in the last two Super Rugby finals outside Ngatai and Sonny Bill-Williams at centre, Horrell's dependability could see him make a starting return from injury against the resurgent Western Force.

''We've managed Andrew Horrell through the last two or three weeks. He's been able to play but we didn't feel he was sharp enough, given the problems he's had with his groin,'' Smith said. ''He's trained well. He's looking good and is ready to go. There's a real opportunity there for him.''

Internally, the Chiefs were enthused by Tom Marshall's first game of the year against the Stormers - his freakish back-heeled flick featuring prominently in highlight reels.

The former Crusaders utility moved to Hamilton in search of more game-time at fullback, but after a solid performance at second five-eighth he is likely to retain the role, and possibly team up with Horrell, this week.

''Tom Marshall was a real positive in his workrate,'' Smith said. ''He hadn't played for a long time. He'd only had about two days training with us.''

After sitting out the dominant victory over the Stormers, where the Chiefs ran in six tries, to rest his elbow, Muliaina is keen to return. His experience could be a valued commodity at fullback, though Gareth Anscombe also impressed in his comeback match.

''It's not too bad at the moment,'' Muliaina said of his elbow. ''I had a lot of fluid out of it over the last couple of weeks. Not playing last week really helped it. I'm trying to build a bit more strength in it. I'm looking forward to hopefully being selected.''

The 33-year-old is happy switching roles but is most comfortable with 15 on his back.''I had a stint at centre in the second year of my contract [in Japan] but it's not a position I've played year in, year out.''